Method of detecting positional dislocation of camera

ABSTRACT

A fixed point for confirmation is photographed by a camera prior to the start of a robot job, to obtain photographing data (S1, S2), a position data is determined from the photographing data (S3), and an error (Δε) between the position data and a reference position data (S4) is determined. When this error (Δε) exceeds a predetermined tolerance (εa), a camera positional dislocation alarm is issued (S6). With this arrangement, the positional dislocation of the camera can be confirmed prior to the start of a job, whereby the job can be safely carried out.

TECHNICAL FIELD

The present invention relates to a method of detecting a positionaldislocation of a camera in a robot system, and more specifically, to amethod of detecting the positional dislocation of a camera by which thepositional dislocation of the camera can be confirmed prior to the startof a job.

BACKGROUND ART

A robot system in which workpieces are photographed by a camera and theposition thereof is recognized thereby is now in practical use forcarrying out an inspection job, assembly job, palletizing job and thelike. The camera is fixed, or mounted on the hand of a robot, for thispurpose, and in particular, when the position of the camera is fixed,assembly jobs and the like cannot be carried out if the position of thecamera is dislocated.

The normal operation of the robot can be prevented by various causes,including, for example, the dislocation of the relative position of therobot and an object, and errors in a teaching program and the like.

Therefore, when a problem occurs, the elements which may be the cause ofthe problem must be individually checked, to specify the cause of theproblem. Of course, the dislocation of the camera is one of the causesof the problem.

In general, although the frequency of dislocation of the position andattitude of a fixed camera is not high, a slight positional dislocationof the camera would disturb a robot job in which the camera isphotographing a distant object. A slight amount of positionaldislocation is difficult to easily determine, but when a job is carriedout by using the robot without checking the positional dislocationthereof, the operator feels uneasy before the start of the job, as if aproblem arises while the robot is being operated, workpieces and thelike may be damaged, and this damage is difficult to recover.

Consequently, the positional dislocation of a camera, and the attitudethereof and the like, must be confirmed prior to the start of a job.

DISCLOSURE OF THE INVENTION

Taking the above into consideration, an object of the present inventionis to provide a method of detecting the positional dislocation of acamera by which the positional dislocation of the camera can beconfirmed by a simple method prior to the start of a job.

To attain the above object, according to the present invention, there isprovided a method of detecting a positional dislocation of a camera in arobot system, which comprises the steps of obtaining photographing databy photographing a fixed point for confirmation by the camera, obtaininga position data from the photographing data, determining an errorbetween the position data and a reference position data, and giving awarning of the positional dislocation of the camera when the errorexceeds a predetermined tolerance.

The fixed point for confirmation is photographed by the camera prior tothe start of a robot job, to obtain photographing data, position data isdetermined from the photographing data, and then any error between theposition data and a reference position data is determined. When theerror exceeds the predetermined tolerance, a camera positionaldislocation alarm is output, whereby the positional dislocation of thecamera can be confirmed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a positional dislocation confirmation program;and

FIG. 2 is a diagram showing the arrangement of a robot system as awhole, embodying a method of detecting the positional dislocation of acamera according to the present invention.

BEST MODE OF CARRYING OUT THE INVENTION

An embodiment of the present invention will be described below withreference to the drawings.

FIG. 2 is a diagram showing the arrangement of a robot system as awhole, embodying a method of detecting the positional dislocation of acamera according to the present invention, wherein a pattern plate 3 isconnected to the arm 2 of a robot 1 and the pattern plate 3 is providedwith a fixed point for confirming the positional dislocation of a camera4. Although almost all positional dislocations of the camera 4 can bedetected by only one fixed point, two fixed points are provided here foran increased detecting accuracy.

The robot 1 is controlled by a robot control unit 10, which controls therobot 1 to position the pattern plate 3 at a reference position todetect the positional dislocation of the camera 4.

Further, an image processing unit 20 is connected to the camera 4 anddetects the positional dislocation of the camera 4 by photographing thepattern plate 3 with the camera 4.

The image processing unit 20 is arranged by using a processor (CPU) 21as the central component thereof, wherein a ROM 22 stores a controlsoftware 22a for processing an image; a program memory 23 stores apositional dislocation confirmation program 23a, to be described laterin detail, for confirming the positional dislocation of the camera 4; adata memory 24 stores the reference position data 24a of the fixed pointof the pattern plate 3 to be photographed by the camera 4; and, a framememory 25 stores the photographing data 25a of the fixed point of thepattern plate 3 photographed by the camera 4 through a camera interface(CINT) 28. This photographing data 25a is processed by an imageprocessing processor 26 and supplied to the data memory 24 as a positiondata 24b.

An interface (INT) 27, used to communicate with the robot control unit10, receives the positional dislocation confirmation command of thecamera 4 from the robot control unit 10 and supplies the positionaldislocation alarm signal or normal position signal of the camera 4 tothe robot control unit 10.

Next, the positional dislocation confirmation program of the camera 4will be described.

FIG. 1 is a flowchart of a positional dislocation confirmation program,wherein numerals prefixed with an "S" indicate the number of steps ofthe routine.

[S1] It is determined whether or not the robot control unit 10 hasissued a command for confirming the position of the camera 4, and whenthe command has been issued, the routine goes to step S2.

[S2] It is determined by the robot control unit 10 whether or not therobot 1 has positioned the pattern plate 3 at the reference position,and when the pattern plate 3 has been positioned there, the routine goesto step S3.

Note, when the pattern plate 3 has been positioned, the robot controlunit 10 supplies a positioning completion signal to the image processingunit 20 through the interface 27.

[S3] The fixed positions of the pattern plate 3 is photographed by thecamera 4 and the resultant data is fetched by the frame memory 25 as thephotographing data 25a, through the camera interface 28. Further, thisphotographing data 25a is processed by the image processing processor 26and stored in the data memory 24 as the position data 24b.

[S4] The reference position data 24a is compared with the position data24b and an error Δε therebetween is determined.

[S5] The error Δε is compared with a tolerance εa, and when the error Δεis greater than the tolerance εa, the routine goes to S6: when the errorΔε is not greater than the tolerance εa, the routine goes to S7.

[S6] Since the error Δε is greater than the tolerance εa, the alarmsignal warning of a positional dislocation of the camera 4 is suppliedto the robot control unit 10.

[S7] A camera position normal signal is supplied to the robot controlunit 10.

Upon receiving the positional dislocation alarm signal, the robotcontrol unit 10 displays the positional dislocation alarm signal of thecamera 4 at a not shown display unit, by which the operator is notifiedof the positional dislocation of the camera. Conversely, when theposition of the camera 4 is not dislocated, the position normal signalof the camera is supplied to the robot control unit 10 and a displaythat the position of the camera is not abnormal is given, and thus theoperator can start a job without anxiety.

Although the fixed point for photographing is provided with the patternplate, and the pattern plate is positioned at the reference position bythe robot, the fixed point may be provided with a fixed location.

Further, although a positional dislocation alarm signal or positionconfirmation signal of the camera is supplied to the robot control unit,and a positional dislocation alarm or the like is displayed at thedisplay unit of the robot control unit in the above description, thesepositional dislocation alarm signals may be supplied to a programmablecontroller (PC) integrally controlling the robot, and processed thereby.

As described above, according to the present invention, since thepositional dislocation of the camera is detected by photographing thefixed position by the camera, whether or not the camera is normallypositioned can be confirmed prior to the start of a job, whereby the jobcan be safely started.

We claim:
 1. A method of detecting a positional dislocation of a camerain a robot system, comprising the steps of:(a) obtaining photographingdata by photographing a fixed point for confirmation by said camera; (b)obtaining position data from said photographing data; (c) determining anerror between said position data and a predetermined reference position;and (d) giving an alarm warning of the positional dislocation of saidcamera when said error exceeds a predetermined tolerance.
 2. A method ofdetecting a positional dislocation of a camera according to claim 1,wherein said fixed point for confirmation is a point set on a patternplate held by the arm of a robot and said robot positions said patternplate at a reference position.
 3. A method of detecting a positionaldislocation of a camera according to claim 1, further comprising thestep of (e) confirming the position of said camera based upon where thefixed point is provided.